The job is a poisoned chalice for the following reason:
The Leave campaign succeeded by convincing their voters that the so-called "threats" of the financial experts weren't important as nobody can predict what will happen. A bit like saying smoking isn't bad for you because nobody can predict what will happen to any particular individual person, or global warming doesn't exist because nobody can be sure that other factors aren't causing the anomalies.
In doing so, they devalued the importance of financial forecasting in the minds of Leave voters.
Now they have started negotiations, the pound has devalued, British stocks have fallen, our economy has been overtaken by France, our credit rating has been downgraded and we have already shown our cards to the other players, the financial forecasters are saying our future looks dire.
So the new PM is in a no win position.
If they stick with the principle of ignoring the financial experts, Britain will face years of depression and austerity and may well never recover. However if they listen to the financial experts and decide it would be suicidal to invoke Article 50 they will get lynched by the Leave voters.
You can't start explaining international finance and it's impact on jobs, money, housing, medicare, pensions, immigration etc to the Leave voters at this stage having just convinced them that it's not important.